1. Field of the Invention
The present invention generally involves the field of technology pertaining to an energy efficient motor brake wherein constant power to a brake is kept off and wherein the electrical circuit pulses the brake to keep the brake unlocked. Batteries, constantly charged with very low voltage, from the main AC power supply, supplies the power drive to brake. A power pulse to the brake immediately activates the brake.
The electrical circuit comprises three phases of electrical power, a transformer, rectifier and monitors. In the event of a failure of any one of the three phases of electrical power for a maximum period of twenty five milliseconds the monitors activate a circuit which in turn locks the brake.
In general, the bi-stable motor brake itself comprises a front flange, a pressure plate operatively associated with and attached to the front flange by means of plurality of fasteners such as cap screws, split lock washers and flat washers, an armature plate parallel to and spaced apart from the flange and pressure plate, a friction assembly operatively associated with and disposed between the armature and pressure plate, a field coil assembly apart from and parallel to the armature plate. A plurality of fasteners such as a combination of studs and hex nuts extend through and hold together the pressure plate, armature plate and permanent magnet field coil assembly.
Coil springs surround the studs and are disposed between the armature plate and field coil assembly.
A cover enclosed all the operative parts previously described and is attached to the flange by any well known fastening device.
The armature plate moves axially responsive to an electrical pulse to lock the brake. The coil springs bear on the armature plate supplying the force to actually move the plate in a "brake-on" position.
When the electrical circuit is off, the coil is de-magnetized and the coil spring expands and compresses the armature plate against the friction assembly in a "brake-on" position.
When the field coil assembly is pulsed with a reverse polarity, the armature plate compresses the coil springs and the permanent magnet holds the armature plate away from the friction plate and the field coil assembly releasing the brake.
2. Description of Prior Art
U.S. Pat. No. 5,185,542 relates to an electromagnetic brake which will latch and hold in either the on or off position when pulsed with a D.C. current.
U.S. Pat. No. 2,421,757 discloses friction devices comprising relatively rotatable faces engaged electromagnetically.
U.S. Pat. No. 3,730,317 disclosed a magnetic coupling wherein one of the coupling members is formed of a readily magnetized material to different polarities to effectuate movement of the coupling members between engaged and disengaged positions.